As is known, a motor vehicle is equipped with rotating electrical machines, in particular an alternator or an alternator-starter.
With reference to FIG. 1, a rotating electrical machine in the form of a reversible alternator of the multi-phase type for a motor vehicle with a thermal engine is schematically illustrated.
Such a reversible alternator is called an alternator-starter.
In a known way, in one operating mode, this reversible alternator converts mechanical energy into electrical energy, in particular for recharging the battery of the motor vehicle and/or for supplying the vehicle accessories with electrical power. In this case, it is said that the reversible alternator is operating in alternator mode, that is to say, as a current generator.
In another operating mode, the reversible alternator converts electrical energy into mechanical energy, in particular for starting the thermal engine of the motor vehicle. In this case, it is said that the reversible alternator is working in starter mode, that is to say, as an electric motor.
Thus, owing to the alternator-starter, the thermal engine of the vehicle can be stopped, for example at a red light or in traffic jams, and said engine can be re-started for example according to a determined or predetermined strategy. This strategy takes into account, for example, the state of the engine gear box and clutch pedal; the engine being stopped when the engine gear box is at the dead point and clutch pedal action relaxed and vice-versa to re-start. This function is known as “stop-start”.
In all cases, the alternator-starter fulfils this function in starter mode in order to save fuel, particularly when driving in town.
The alternator-starter, depending on its power, can also fulfil other functions in starter mode, that is to say, when it is working as an electric motor.
For example, as described in document WO 02/060711, it can be used to drive an accessory, such as an air-conditioning compressor, when the vehicle has stopped at red lights, or to assist in starting up an accessory, such as a turbo compressor.
It can be used to temporarily move the vehicle when parking.
As described for example in document WO 02/080334, it can prevent the thermal engine of the vehicle from stalling (function known as BOOST function) and, during braking or deceleration of the vehicle, charge one or more energy stores such as “super capacitors” or ultra-capacitors.
FIG. 1 illustrates a separate alternator-starter 1 of the type described in document WO 01/69762 to which reference should be made.
This alternator-starter 1 is mounted here instead of a traditional alternator and comprises a drive component in the form of a pulley 20 integrally joined to a shaft.
This alternator-starter 1 is connected to the crankshaft of the thermal engine of the motor vehicle here via its drive component 20 belonging to a movement transmission device situated between the alternator-starter and the thermal engine.
More precisely, this pulley 20 is connected to a pulley 21 of the crankshaft of the thermal engine by means of at least one belt 40.
This alternator-starter 1, as is more clearly visible in FIG. 2, which is a simplified cross-sectional view of the alternator-starter, comprises a casing 10 carrying a stator 16 surrounding a rotor 4 integrally joined to a shaft 14, of axis X, carrying the pulley 20 at its front end.
The stator 16 comprises an annular housing 18 in the form of a stack of metal sheets with recesses forming grooves for mounting armature coils 5 having chignons extending on both sides of the ends 24, 26 of the housing 18.
The housing 18 is therefore made of ferromagnetic material.
A small air-gap exists between the internal periphery of the housing 18 and the external periphery of the rotor 4.
The alternator in FIG. 1 comprises three phases. Alternatively, it comprises more than three phases, for example five, six or seven phases.
Each phase comprises at least one armature coil 5.
These coils 5 are angularly offset and connected in a star or triangle as is visible in FIG. 1. They are connected at their output to an alternating current rectifying device 8 as described below.
The coils or windings 5 can be implemented with conducting wire wound in the recesses of the stator housing, for example in a corrugated way or in the form of coils wound around a tooth of the stator housing, or with conductor elements in the shape of bars mounted in the recesses and joined together for example by welding to form networks.
Alternatively, each phase comprises at least two coils mounted in series or in parallel with the presence in this case of two rectifier bridges mounted in parallel and star-star or star-triangle or triangle-triangle connections of the triphase coils of the phases. One or more coils 5 are therefore mounted in each recess of the stator housing.
The shaft 14 of the rotor 4 is mounted centrally to rotate in the casing by means here of ball bearings without a reference symbol.
The rotor 4 illustrated in FIG. 2, as described in document EP A 0 515 259, is a clamp rotor comprising ferromagnetic polar wheels 50, equipped with flanges having teeth on their external periphery.
A field coil 41 is mounted between the flanges. Permanent magnets can be inserted between the teeth of the polar wheels, as described for example in document FR A 2 793 085.
Alternatively, the rotor has projecting poles, a field coil being mounted around each projecting pole belonging to the rotor housing, for example in the form of a stack of metal sheets.
Alternatively, this rotor with projecting poles also comprises permanent magnets alternating circumferentially with the field coils as described in document WO 02/054566.
The casing comprises at least two parts perforated for circulation of the air. One of these parts is called the front bearing and the other part is called the rear bearing. The bearings are metallic and connected to the ground of the motor vehicle.
The rotor then supports, at least one of its axial ends, an internal fan, without a reference symbol in FIG. 2, to cool the alternator, as is visible in the two documents WO 02/054566 and EP A 0 515 259.
The rear bearing supports a brush holder illustrated by a rectangle with dotted lines in FIG. 2, whose brushes 42, 43 (FIG. 1) cooperate with slip rings 44, 45 supported by the rear end of the shaft 14. These rings are connected electrically to the ends of the field coil(s) 41.
When the thermal engine of the motor vehicle rotates, the pulley 20, shaft 14 and rotor 4 are also driven in rotation and the coil(s) 41 are supplied with electrical power by means of the brushes. The inductor rotor 4 is then magnetized, a magnetic field is created and the coils 5 of the induced stator generate an induced AC current.
The current rectifying device 8 in FIG. 1, in a synchronous manner, converts this induced AC current into DC current in order to charge the battery and/or supply the electrical consumers in the on-board electrical network of the vehicle.
This rectifying device 8 here belongs to an electronic control and power unit 2, which also comprises a management module 9, which receives data enabling the position and rotational speed of the rotor 4 of the alternator-starter 1 to be determined. This data, for example, is data provided by sensors 11, such as Hall-Effect sensors. These sensors are mounted for example on an angularly adjustable sensor holder as described in document WO 01/697 cited above (see for example FIGS. 7 and 9). Alternatively, the sensors 11 are replaced by a resolver.
The unit 2 here is remote in relation to the alternator-starter, a cable and connectors providing the link between the rear bearing of the alternator-starter 1 and the unit 2.
The rectifying device 8 comprises drivable elements for rectifying the current, such as transistors 7-7′ mounted in parallel on diodes 6-6′ as described for example in document FR-A-2 745 445. The transistors are advantageously MOSFET type power transistors and constitute static type switches, which can be controlled, in starter mode, by acting on the grids of these transistors. These transistors 7-7′ integrate by design the diodes 6-6′.
The current rectifying device 8 belongs to a power stage of the unit 2. It constitutes a reversible power converter which assures the driving when functioning in starter mode and the synchronous rectifying in alternator mode.
The voltage regulator of the alternator-starter 1 here also belongs to the module 9. For the record, it will be recalled that the voltage regulator drives the field coil 41 of the rotor 4 via the brushes 42, 43, the slip rings 44, 45, a commutator and wire connections as described in document FR 2 710 199 for example. In FIG. 1 the electrical line EXC connects the voltage regulator of the module 9 to the brush 43, itself connected to one end of the coil 43, whose other end is connected to the track 44 and to the brush 42 connected to the ground.
The module 9 thus manages voltage regulation when the machine functions in alternator mode and also the power in starter mode and alternator mode. This module 9 can also manage safety functions and monitor the state of the battery and the state of the battery charge and/or assure other functions, particularly during the braking or deceleration of the motor vehicle as described in document WO02/080334 cited above.
This module 9 comprises drivers to drive the grids of the transistors 7-7′. Thus, the module 9 is configured, via the drivers, to deliver as output signals A, B, C and A′, B′, C′ to the grids of the transistors 7.
This module 9 may be equipped with a device to protect against over-voltages as described in document WO 2005/025025 to which reference should be made.
As described in this document and as is visible in FIG. 1, each output of phase coil 5 is associated with two transistors 7-7′ of the MOSFET type with integrated diodes 6-6′. These two transistors 7-7′ belong to an arm or branch 81, on the one hand, situated between an electrical power supply line 83, known as the positive line, connected to the positive terminal 82 of the battery B and to the positive potential 85 of at least one on-board electrical network of the vehicle and, on the other hand, a line 84, known as the negative line, connected to the ground.
The number of arms or branches 81 depends on the applications and particularly on the number of phases of the alternator-starter.
The transistors 7-7′, constituting controlled power switches, are thus grouped by pairs of transistors connected to the same output of a phase coil 5. The power transistor 7′, 6′ connected to the positive line 83 is called a “high side” transistor, while the power transistor 7, 6 connected to the negative line 84 is called a “low side” transistor.
The drivers specifically act on the grids of the transistors 7-7′ to make them “conducting” (transistor closed) or blocked (transistor open). These drivers receive data provided by the resolver or the position sensors 11 of the rotor 4 together with logic type data for validating the alternator mode and for validating the starter mode.
For more precise details, reference should be made to document WO 2005/025025 cited above.
The management module 9, in the way cited above, is configured for controlling the transistors 7-7′ and for delivering signals A, B, etc to the grid of the latter to make these transistors “conducting” or open; each driver being associated here with two signals A, A′-B, B′-C, C′.
In starter mode, the device 8 is an inverter, which supplies the coils 5 of the stator 16 phases with power; the transistors 7-7′ being then driven. For example, an advantageously maximum DC current is imposed in the field coil(s) of the rotor, constituting the inductor of the alternator, and de-phased signals which are ideally sinusoidal and alternatively trapezoidal or square are delivered to the coils of the stator phases.
In alternator mode, the device 8 is a rectifying current bridge to rectify the AC current of coils 5 of the phases to DC current. The transistors 7-7′ are not driven in this alternator mode; the diodes 6-6′ are then active.
The module 9 can also receive data about the temperature of the alternator-starter and/or the rectifying device 8 or receive data from the engine control unit (ECU). In this FIG. 1, the electrical connection line to this engine control unit is represented by the reference symbol ECU.
This module 9 thus comprises hardware resources, in particular a micro-processor and memory, a multi-channel connector, and possibly software resources, particularly one or more stop/re-start algorithms to fulfil these various functions. These various functions can also be fulfilled on the basis of ASIC-type circuits or in a general manner by cabled logic.
The module 9 is supplied with power by the battery B of the vehicle to which it is connected electrically by means of a switch 12 controlled, for example, by the ignition key of the vehicle.
The module 9 optionally comprises means for recognizing a coded signal authorizing starting the vehicle engine and drives the MOSFET transistors 7-7′ only if it receives the coded signal.
Alternatively, the alternator is not reversible as described in document EP A 0 515 259 for example.
In this case the current rectifying device is a bridge of diodes.